keel Lift vs side Force help???

Discussion in 'Sailboats' started by lordrailie, Jul 3, 2006.

  1. lordrailie
    Joined: Jul 2004
    Posts: 14
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    Location: SPAIN

    lordrailie Junior Member

    I'm trying to calculate the area needed for a keel for a 60 foot yacht.

    My sail plan give a side force of 9312 N at a Apparent wind angle of 27º and a wind speed of 9.5m/s, so if I'm not wrong I'm looking for a keel that makes a lift of a 9312 N at a yaw angle about 5º.

    The thing is that I'm getting very low Lift values for my keel

    The data I'm using is:

    Tk 1,7
    Chord Top C1 2
    Chord Bottom C2 1,5
    Sweep Angle 21

    AR keel 0,971428571
    Main Chord Keel 1,75
    Taper Ratio λ 0,75
    Area Keel 2,975

    CL 2d foil 0,11
    α degrees keel 5
    CL Keel 0,179807692
    CDI 0,010593898

    And getting those lift and drag values, but those are not large enogh, and the keel is quite large already, and the sction is a naca 63A012

    Drag 186,7417686
    Lift 3169,523279

    What I'm doing wrong....

    Thanks
     
  2. jehardiman
    Joined: Aug 2004
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    jehardiman Senior Member

    63A012 and AOA=5 degrees? Offhand, I think you are out of the drag bucket. Try it with a NACA 0012. remember that low drag is not equal to high lift.
     
  3. lordrailie
    Joined: Jul 2004
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    lordrailie Junior Member

    Theoretically the lift formula should be

    L= 1/2*Cl* p*S*V^2 Where p is density

    And the Cl obtained from:

    Cl= Cl2d*α/(1+(2/AR))

    AR=Tk/C
    where Tk is draft and C is chord

    but .... which Tk should I consider, the depth from bottom of hull to bottom of keel or double this size (mirror with hull),

    Am I right.??..

    Where can I find a sample of a calculation of lift and drag of a keel, done by "hand"

    Regards
     
  4. Raggi_Thor
    Joined: Jan 2004
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    Location: Trondheim, NORWAY

    Raggi_Thor Nav.arch/Designer/Builder

    You can mirror it, OK.
    Does that help?
     
  5. lordrailie
    Joined: Jul 2004
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    lordrailie Junior Member

    If I use the whole span inclduing the mirror, the results get a lot better, but i'm not sure if they are right....

    Below are the results (and data used), and the lift is 3 times larger than using only the span of the keel below the hull....

    Tk 3,4
    Chord Top C1 1,7
    Chord Bottom C2 1,25
    Sweep Angle 21

    AR keel 2,305084746
    Main Chord Keel 1,475
    Taper Ratio λ 0,735294118
    Area Keel 5,015

    CL 2d foil 0,11
    α degrees keel 5
    CL Keel 0,294488189
    CDI 0,011975647

    Drag 355,8513674
    Lift 8750,593853

    Thanxs
     

  6. lordrailie
    Joined: Jul 2004
    Posts: 14
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    Location: SPAIN

    lordrailie Junior Member

    Any help

    any one can give mi a hint?
     
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